Borrowable

+ borrow()

+ returnItem()

Material

# materialId: String

# title: String

# publicationYear: int

+ displayDetails(): void {abstract}

- materials: List<Material>

+ addMaterial(material: Material): void

+ removeMaterial(material: Material): void

+ displayAvailableMaterials(): void

- author: String

+ displayDetails(): void

- issueNumber: int

+ displayDetails(): void